Precast reinforced concrete bridges are per se known. For example, see US. Pat. No. 3,482,406. The bridge disclosed in said patent is more theoretical than practical in that few details are given as to how the spans are connected to each other. Further, the precast spans are provided with an arch shape which is non-circular at least in part.
It is known from U.S. Pat. No. 3,478,481 to connect adjacent spans of reinforced concrete by welding the metal reinforcement together. It is known to make tunnels of precast concrete by precasting the tunnel into halfs which are then joined together.
There is a need for a simple and inexpensive design of a precast bridge whereby the components may be delivered by a truck to the site and erected in one day with minimal skilled labor.